At standard clock your 9800GT cards should run 24/7 with no temp problems.

Not only at standard clock. 9800gt works well quite overclocked, with no additional fans or custom cooling systems.
I use RivaTuner program for overclocking and this is the results:

The 9800gt fan is manually set to 44%

What's the highest stable OC (GPU and VRAM) you've gotten at 100% fan speed?

---

me@rescam.org

If anybody needs detailed instructions on how to make dummy plugs, just let me know.

How to make VGA Dummy.

What's the highest stable OC (GPU and VRAM) you've gotten at 100% fan speed?

Short answer:
Maximum stable overclocking of nVidia 9800GT:
GPU core clock - 738 MHz
GPU shader domain - 1836 MHz
GPU memory clock - 972 MHz

Long answer:
The speed of the 9800gt fan does not affect much the stability, when overclocking.
When I hit 2000 MHz shader clock / 800 MHz GPU core clock - SETI@Home_6,08_cuda immediately reports "COMPUTATION ERROR".
At 1890 shader / 756 core / 999 memory clocks, SETI@Home_6,08_cuda works normal for about 10~30 minutes, and BANG! - "COMPUTATION ERROR". On the graph, only the drop in temperatures at 15:50:13 is normally completed work unit. Every other drop in temperatures until 16:59:02 is WU ended with "COMPUTATION ERROR".

NOTES:
1. Beginning with drivers ver. 190,38 Riva Tuner 2,24 no longer automatically recognize the driver and you have to manually enter the driver version in the Riva Tuner "POWER USER" tab. (Riva Tuner/System -> ForceDriverVersion...)
2. The fan settings in Riva Tuner after 190,38 are "UPSIDE DOWN" (i.e. 100% fan = fan off (0 RPM) and 25% fan = 75% of the maximum RPM)

And because I hate loud fans, now I run 9800gt overclocked with fan set to 21% of the max RPM (79% on the graph) and the GPU temperature is ~62º Celsius.

---

Cogito Ergo Sum

Thanks Claggy
I knew the answer to this problem was on the boards here somewhere.Your cc_config file did the trick and all GPU's are now working.

Regards
Brodo